Distribution of [3H]-corticosterone in urine, feces and blood of male Sprague-Dawley rats after tail vein and jugular vein injections.

The present study aimed to investigate the time-course and distribution of [(3)H]-corticosterone in urine, feces and blood of male Sprague-Dawley rats after intravenous administration of a low dose (1 microCi), and to investigate whether different intravenous routes of administration may affect the dynamics of excreted [(3)H]-corticosterone in the feces. One microCi [(3)H]-corticosterone was injected intravenously either through the tail vein in manually restrained rats or through a jugular vein catheter three days after surgical implantation. Urine and feces were collected at different time points over 78 h from the rats injected in the tail vein, and blood and feces were collected over 48 h from rats injected in the jugular vein. In the blood, radioactivity peaked immediately and decreased rapidly within 90 minutes. The radioactivity was excreted in urine within six h and in feces after at least 12 h. Sixty percent of the radioactivity was detected in the urine and 40% in feces during the study period of 78 h. The detected amount of radioactivity in feces was higher and displayed a more pronounced peak 12 h after injection when the substance was administered through a jugular vein catheter compared to tail vein injection. The data obtained in the present study may serve as an important benchmark when choosing time points for fecal collection for quantification of corticosterone or corticosterone metabolites as a non-invasive measure of preceding HPA-axis activation.